Mitochondrial DNA Lineages and Haplotype Diversity of Elite Kenyan Athletes

Abstract

Mitochondrial DNA (mtDNA) codes for elements of the mitochondrial respiratory chain. The maternal inheritance of mtDNA has enabled construction of detailed phylogenies. Analysis of key polymorphisms from these phylogenies allows mtDNA to be assigned to haplogroups. Recently, it has been shown that certain mtDNA haplogroups differ in frequency between elite Finnish endurance and sprint athletes (Niemi et al. Eur J Hum Genet 13(8):965–9, 2005), although we have previously shown that mtDNA haplogroups were not associated with elite Ethiopian athlete status (Scott et al. Comp Biochem Physiol A Mol Integr Physiol 140(3):497–503, 2005). PURPOSE: To compare the frequencies of mtDNA haplogroups found in elite Kenyan athletes with haplogroup frequencies in the general Kenyan population. METHODS: DNA samples were obtained, with ethics approval, from 221 national level Kenyan athletes (N), 70 International Kenyan athletes (I), and 85 members of the general Kenyan population (C). mtDNA was classified into haplogroups by sequencing 340 bases of hypervariable sequence (HVS I), and by genotyping known restriction sites (3592 HpaI, 10394 DdeI, and 10397 A luI). Frequency differences between groups were assessed using contingency chi-square tests. RESULTS: All groups displayed similar high levels of haplotype diversity, based on HVS I haplotypes (C = 0.99, N = 0.99, I = 0.99). However, the haplogroup distribution of International athletes differed significantly from Controls (P = 0.027), with International athletes showing a greater proportion of L0 haplogroups (C = 15%, N = 18%, I = 30%) and a lower proportion of L2 haplogroups (C = 18%, N = 10%, I = 7%) relative to Controls. Although a disproportionately high number of International athletes originated from the Rift Valley province, this province did not differ in haplogroup distribution from other regions (P = 0.715). Haplogroup distribution did not differ between Bantu and Nilote language speakers (P = 0.193). CONCLUSIONS: International athletes, consisting of many of the most successful athletes in Kenyan athletic history, differed in their mtDNA haplogroup distribution relative to the general Kenyan population. They displayed an overrepresentation of L0 haplogroups, and an under-representation of L2 haplogroups. This may suggest that certain mtDNA haplogroups are influential in elite Kenyan distance running, although population stratification cannot be ruled out. Despite the over-representation of L0 haplogroups relative to controls, only 30% of Kenyan international athletes belonged to this haplogroup, highlighting the complexity of the elite athlete phenotype.